11 Biology Chapter 6 Question Answers

Important Terms on Anatomy of Flowering Plants

Axillary bud: The buds which are present in the axils of leaves (Consist of cells left behind from shoot apical meristem) and are responsible for forming branches of flowers.

Permanent tissues: The permanent tissues are derived from meristematic tissue, are composed of cells, which have lost the ability to divide and have become structurally and functionally specialised.

Anatomy

Anatomy is the study of internal structure of organisms. Plant anatomy includes organisation and structure of tissues. Tissue is a group is cells having a common origin and usually performing a common function. Its wall is made up of cellulose. It performs the functions like photosynthesis, storage, secretion.

Collenchyma: It is formed of living, closely packed cells. Its cells are thicknened at the corners due to depositon of celluose and pectin. It provide mechanical support to the growing parts of the plant. It is either found in homogenous layer or patches.Sclerenchyma: It is formed of dead cells with thick and lignified walls. Provide mechanical support to organs. They have two types of cells: fibres and sclereids.

Xylem

Xylem consists of tracheids vessels, xylem fibres and xylem parenchyma. It conducts water and minerals from roots to other parts of plant.

Tracheids-Tube like cells with thick and lignified walls and tapering ends; dead, without protoplasm.

Vessel-long cylindrical structure made up of many cells with large central cavity, devoid of protoplasm. Present in angiosperms.

Xylem parenchyma-living and thin walled; cell walls made up cellulose, store food material in form of starch or fat. Radial conduction of water takes place by ray parenchymatous cells.

Protoxylem: The first formed primary xylem elements.

Metaxylem: The later formed primary xylem.

Endarch: Protoxylem lies towards the centre and metaxylem towards the periphery of the organ; in stem.

Phloem

Phloem consists of sieve tube elements, companion cells, phloem fibres and phloem parenchyma; Phloem transports the food material from leaves to various parts of the plant.

Sieve tube elements: These are long tube like structures arranged longitudinally, associated with companion cells. Its end walls are perforated to form sieve plates and functions of sieve tubes are controlled by the nucleus of companion cells.

Companion cells are specialised parenchymatous cells associated with sieve tube elements and connected with sieve tube elements by pit fields present between their common longitudinal walls. It help maintain pressure gradient in sieve tubes.

Phloem Parenchyma is made up of elongated, tapering cylindrical cells with dense cytoplasm and nucleus. Its cell wall made of cellulose with pits through which plasmodesmatal connections exist between cells and store food material.